The premotor cortex (Brodmann’s Area 6) is located in the frontal cortex of the primate brain and lies anterior to the central sulcus and the primary motor cortex (M1) with the overarching functions of planning possible movement trajectories, spatial and sensory guidance of movements, as well as comprehending the actions of others. The premotor cortex receives afferent and sends efferent signals to the primary motor cortex, prefrontal cortex, and parietal cortex. In addition, it also sends projections to the spinal cord, making up a portion of the corticospinal tract, as well as to the striatum and thalamus in the brain (Purves & Williams, 2001). The premotor cortex can be divided into both medial-lateral functional divisions and the lateral premotor cortex can be subdivided into ventral-dorsal areas. The majority of the lateral premotor cortex is dedicated to understanding guided movements whereas the medial portion of the premotor cortex is focused on internal, self-initiated movements (Purves & Williams, 2001). While both the ventral and dorsal premotor cortices are active directly prior to a goal-oriented movement, they both respond to particular stimuli. For example, the ventral premotor cortex (PMv) receives a variety of visual and somatosensory inputs and is implicated in decision-making of the best movement, and it is also selectively activated to …show more content…
determine the 3D shape of an object to allow for successful grasping (Hoshi & Tanji, 2006, 2007). In contrast, the dorsal premotor area (PMd) is most active in response to visuomotor-association tasks (accurately reach for target in space) (Hoshi & Tanji, 2006). In order to successfully complete a goal-oriented movement, the brain must compute information about the location of the target in an extrinsic coordinate frame (fixed axis independent of the body) into an intrinsic coordinate frame that provides information about the location of the limbs and joints in space and ultimately determines muscle activation patterns to allow for task completion (Kakei, Hoffman, & Strick, 2003). In recent years, there has been debate about the coordinate frame used in the premotor cortex, with evidence currently showing a mixture of intrinsic-like and extrinsic-like coordinate frames in the various areas (Kakei et al., 2003). In order to test the hypothesis that neural activity in the premotor cortex relates to planning movements in an extrinsic coordinate frame, one must design an experiment that would allow for the recording of individual neurons in the premotor cortex as well as provide a sufficient delay period were one would be subconsciously planning the movement. Additionally, the behavioral task would require movements in various, repeatable direction as well as a variety of hand postures or arm movements to allow for discernibility of the various coordinate frames. A possible experiment would be train rhesus macaques or another non-human primate species to perform a visually directed reaching movement, such as a modified paradigm of Hoffman, 1986 and Kakei, 2001 and 2003. The animal could be trained to make wrist movements using a 2-degree-of-freedom manipulandum (to monitor flexor-extensor and radial-ulnar movements), whose movement would correspond to a cursor on a computer screen that would be placed at eye level of the animal. To begin, the monkey would be required to move and briefly hold the cursor onto a large circle in the middle of the screen. A peripheral target would then appear on the screen, in addition to the center target and remain there for three seconds, to ensure enough time to observe the planning in the premotor cortex. After the three seconds, the center target would be removed, signaling the animal to use the manipulandum to move the cursor to the peripheral target. The animal would then have to hold the peripheral target for 1 second, until the peripheral target disappeared, signaling the end of the trial. The peripheral targets would be located equidistant from the center at 20-degree intervals, allowing for a total of 20 different peripheral targets. Additionally, the monkey would be trained to perform this task with both hands, as well while holding hand in a supinated, pronated, or intermediate posture. This method would allow for the best determination of each neurons preferred direction, as well as determination of the coordinate frame. Following successful training, the animal would then receive surgery to implant electrodes to record neural activity from both the premotor cortex as well as the primary motor cortex.
Placement of electrodes could also be categorized based on medial-lateral and ventral-dorsal premotor cortex placement to determine regional differences in coordinate frames. Additionally, electrodes could be placed into the hand, wrist, and arm of the monkey to allow for EMG recordings of the muscles. Once the animal has recovered from surgery and has retrained briefly on the behavioral task, the experimental trials could
begin. The data collected from this experiment would allow for determination of preferred direction of each neuron in each hand position. From this, the authors could then compare the shifts between the hand positions to determine the coordinate frame, as if the neurons are indeed extrinsic, then the preferred direction would not change even when hand position changed. In order to support the hypothesis that premotor cortex is involved in planning in extrinsic coordinate frame, the researchers would be required to break down the experiment into various timeframes: baseline (initial move cursor to center target and holding it there), planning (as soon as peripheral target appears directly up until the center target disappears), movement (from when the center target disappears to when the cursor reaches the peripheral target), and the hold (from when cursor touches peripheral target until it disappears). The authors would want to focus on the “planning” phase to determine the overall coordinate frame of premotor cortex as well as any regional differences. While this would provide more information than simply the planning phase coordinate frame, it would allow for one to observe the activity of the premotor areas during movement as well as if there are any changes in the coordinate frame. Overall, this type of experiment would provide information about the coordinate frame of the entire premotor cortex, as well as the subareas. Additionally, it could reveal where coordinate transformations take place and whether or not the timing of the movement (i.e. planning versus movement, versus hold) alters the coordinate frame of the same area. It would also be interesting to view this in a sequence of targets, to determine if certain patterns of activation of rise if one is to move their hand to the right to 180-degrees, then up to 90-degrees. It would also be critical to determine if the areas respond differently depending on the type of movement made (i.e. would coordinate frame change for PMv if a grasping task was made instead of a simple arm movement) References Hoffman, D.S., & Strick, P.L. (1986). Step-tracking movements of the wrist in humans. I. Kinematic analysis. J Neurosci, 6(11), 3309-3318. Hoshi, E., & Tanji, J. (2006). Differential involvement of neurons in the dorsal and ventral premotor cortex during processing of visual signals for action planning. J Neurophysiol, 95(6), 3596-3616. doi: 10.1152/jn.01126.2005 Hoshi, E., & Tanji, J. (2007). Distinctions between dorsal and ventral premotor areas: Anatomical connectivity and functional properties. Curr Opin Neurobiol, 17(2), 234-242. doi: 10.1016/j.conb.2007.02.003 Kakei, S., Hoffman, D.S., & Strick, P.L. (2001). Direction of action is represented in the ventral premotor cortex. Nat Neurosci, 4(10), 1020-1025. doi: 10.1038/nn726 Kakei, S., Hoffman, D.S., & Strick, P.L. (2003). Sensorimotor transformations in cortical motor areas. Neurosci Res, 46(1), 1-10. Purves, D., & Williams, S.M. (2001). Neuroscience (2nd ed.). Sunderland, Mass.: Sinauer Associates.
The data was recorded for ten minutes. The last segment in the data collection was to analyze the effects of direct electrical stimulation. The hook electrode was disconnected and two electrode needles were inserted about five mm from each end of the gastrocnemius muscle. Starting at the maximum voltage from the first experiment, voltage was slowly increased until a twitch appeared. Then voltage was set to ten times the maximum voltage from the first experiment.
In “The Brain on trial”, David Eagleman (2011) recounts the horrifying events which occurred on August 1, 1966. Charles Whitman entered the University of Texas with a rifle and secured himself in the bell tower. He then proceeded to shoot and kill 13 people and injure 32 more. Whitman was also shot and killed; however, during his autopsy it was discovered that a tumor was pressing against his amygdala. According to Eagleman, “The amygdala is involved in emotional regulation, especially of fear and aggression” (2011). Therefore, Whitman was possibly experiencing a fundamental change in his emotions and personality due to the tumor. Though Whitman did not survive, his case still poses questions as to whether or not he should be held accountable for his actions; moreover, should Whitman have received the maximum punishment for the murder he committed? Charles Whitman may not have had control over the feelings of “rage and irrational thoughts” (2011) he was experiencing; however, the precision of the attack indicates he was well aware of the actions he was committing.
...e in the brain to deliver electrical stimulation to targeted areas that control movement (mayoclinic.com, 2013).
The medial dorsal nucleus of the thalamus is situated in areas 4 and 6, that is, located in the front of the motor and premotor cortices of the frontal lobe. The medial part of this nucleus (magnocellular part) projects to the ventral medial orbital portion of the prefrontal lobe (Kringelbach, 2005). This particular portion of the prefrontal cortex is called the orbitofrontal cortex of the brain and, it consists of Brodmann area 10, 11 and 47. It receives inputs from the ventral visual stream, and, inputs from the taste, somatosensory and olfactory receptors (Kringelbach, 2005).
Everything that is real is a lie except your thoughts. If someone approached you with this statement you would assume they are insane and you would try to convince them that you are real and the world is real. As you begin to try to prove reality you begin to question yourself, under what circumstances do we understand reality? As we acknowledge what we believe to be realities, we form conclusions and assurances about our own existence and the existence of everything around us. Because our existence is assured through our perception of reality, we believe to be part of an existing real world. The existence of the real world is based upon belief and cannot be proven. The existence of the real world originates from our brains. Reality is dependent of our perception, experiences, senses, and reasoning.
Firstly, there is various of sensing activities as in seeing and hearing as in a sense of understanding of what is seen and heard. Secondly the sense of feeling in numerous parts of the body from the head to the toes. The ability to recall past events, the sophisticated emotions and the thinking process. The cerebellum acts as a physiological microcomputer which intercepts various sensory and motor nerves to smooth out what would otherwise be jerky muscle motions. The medulla controls the elementary functions responsible for life, such as breathing, cardiac rate and kidney functions. The medulla contains numerous of timing mechanisms as well as other interconnections that control swallowing and salivations.
Prefrontal Cortex The prefrontal cortex is the most anterior portion of the frontal lobe. It responds mostly to stimuli signaling the need for movement, however it is also responsible for many other specialized functions. It receives information from all sensory systems and can integrate a large amount of information (Kalat 2004). Studies have shown that the prefrontal cortex is responsible for working memory. Working memory is defined as "the information that is currently available in memory for working on a problem" (Anderson 2005).
Schurger, A., Sitt, J. D., & Dehaene, S. (2012). An accumulator model for spontaneous neural activity prior to self-initiated movement. Proceedings of the National Academy of Sciences, 109(42), E2904-E2913. Retrieved March 21, 2014, from http://dx.doi.org/10.1073/pnas.1210467109
The frontal lobe comprises a third of the brain and it enables us to engage in higher cognitive functions such as planning and problem solving (Jonides & Smith, 1999). The frontal lobe is divided into 3 regions, the motor cortex, premotor cortex, and prefrontal cortex. The motor cortex is located in the precentral gyrus and directs fine motor coordination. The premotor cortex is involved in planning, organizing, and integrating body movements. The prefrontal is involved in executive functions, including short-term memory, working memory, decision making, and prioritizing behaviors (Wilson, 2003). Some of the frontal lobe disorders than can cause brain damage and behavioral changes are Huntington’s disease, infection, stroke, tourettes, dementia, epilepsy, Parkinson’s disease, tumors, closed head injury and traumatic brain injury (Chow, 2000).
The first implant was a brain reading chip with micro electrode array that was placed at the leg area of the motor cortex of the monkey’s brain. This chip has around 100 electrodes in it. Those who don’t know, motor cortex is the area in our brain where planning and execution of all voluntary movements in our body is done.
Mathematicians, medical doctors, neuroscientists, computer scientists, and a monkey are sitting in a room, they figure out how to remap the brain of paralyzed patients. This is no joke and was done by a team of researchers in 2002 at Brown University. Before a study like the aforementioned came along many would have ask what do a mathematician and a neuroscientist have in common. This is Johansson’s point; we have t...
Prevosto, V., & Sommer, M.A. (2013). Cognitive Control of Movement Via the Cerebellar-Recipient Thalamus. Frontiers in Systems Neuroscience, 7, 1-8.
M.M. Merzenich, R. N. (1984). Somatosensory cortical map changes following digit amputations in adult monkeys. Journal of Comparative Neurology, 224(4): 591-605.
“Maturation of the Prefrontal Cortex.” Office of Population Affairs, n.p. N.d. Web. 17 February 2012.
The human body is divided into many different parts called organs. All of the parts are controlled by an organ called the brain, which is located in the head. The brain weighs about 2. 75 pounds, and has a whitish-pink appearance. The brain is made up of many cells, and is the control centre of the body. The brain flashes messages out to all the other parts of the body.